Wellbores are formed in subterranean formations for various purposes including, for example, extraction of oil and gas from the subterranean formation and extraction of geothermal heat from the subterranean formation. Wellbores may be formed in a subterranean formation using various types of drill bits along with other wellbore tools. The downhole environment can be harsh, with temperatures as high as 175° C. or more, pressures as high as 100 MPa or more, and the presence of corrosive fluids, such as H2S and CO2. Wellbore tools and the components thereof must be able to withstand such extreme pressures, temperatures and corrosive fluids. Furthermore, drilling of the subterranean formation utilizes solids-laden drilling fluid and generates extensive debris in the form of formation cuttings, all of which may be carried within the pressurized drilling fluid. Wellbore tools may be subjected to prolonged contact with such abrasive, pressurized drilling fluid.
Many downhole tools include components that need to be isolated from exposure to pressurized drilling fluid. Thus, seals are provided between adjacent components of such tools to prevent the pressurized drilling fluid from flowing between the adjacent components. In some tools, the adjacent components may be configured to move relative to one another. Seals between such components are referred to as “dynamic” seals, whereas seals between adjacent components that do not move relative to one another are referred to as “static” seals. The seal is established by providing a fluid-tight joint between the components that is intended to prevent migration of liquids and/or gases through the interface between the components. Wellbore tools commonly utilize various polymeric, elastomeric, and metal seals to provide both static and dynamic sealing between stationary and moving components, respectively.
For metal-on-metal seals, soft metals such as copper and lead are commonly used. Other examples of metal-on-metal seals used in wellbore tools include shape memory alloys that exhibit one-way shape memory or two-way shape memory behaviors. Shape memory alloys exhibiting “remembered” states and deformed shape memory alloys may return to the “remembered” states when heated.
Once drilling and forming operations of wells are completed, downhole assemblies often use completion tools to extract natural resources from the subterranean formation for long periods of time. Therefore, completion tools often require components that can perform for at least two to twenty years. As discussed above, downhole environments can be harsh, with temperatures as high as 175° C. or more, pressures as high as 100 MPa or more, and the presence of corrosive fluids, such as H2S and CO2. Completion tools and the components thereof must be able to withstand such extreme pressures, temperatures, heavy brines, and corrosive fluids for as long as possible. Previously known seals, such as, elastomeric and copper metal seals are not known to withstand such extreme environments for the requisite time periods and often require multiple replacements over a life of the well.